POX Activity Research Articles

Exogenous jasmonic acid enhances oxidative protection of Lemna valdiviana subjected to arsenic

Oxidative damage is one of the most harmful effects arising from arsenic (As) toxicity in plants. Herein, the role of exogenous jasmonic acid (JA) in the modulation of As-induced oxidative stress in Lemna valdiviana was investigated. Plants were grown for 24 h in Clark’s nutritive solution containing As (4.0 mg L−1) or As + JA (50, 100, 250 and 500 µM). Chlorophyll a and b content decreased under As stress, either in isolation or associated with JA. The decreased chlorophyll a/b ratio in As-exposed plants was recovered by JA treatment at 100 µM. The carotenoid content was higher in plants exposed to As compared to controls and lower when it was associated with JA. Arsenic triggered the accumulation of O2•− and H2O2, in addition to severely increasing lipid peroxidation. Application of JA in As-grown plants resulted in lower O2•− content and lipid peroxidation than in those grown under As alone, as a result of enhanced SOD activity. On the other hand, H2O2 accumulation was increased by JA in As-stressed plants, associated with higher CAT, POX and GPX activity. The As content and bioaccumulation factor (BF) were improved by application of JA in the nutritive solution at 250 and 500 µM. Our findings indicate that JA modulates the pigment balance, thereby fine-tuning energy dissipation as well as alleviating As-induced oxidative damage in L. valdiviana through modulation of ROS homeostasis and improvement of the antioxidant enzymatic system, allowing increased accumulation of As without showing major damage.

Reactive oxygen species and reactive nitrogen species induce lysigenous aerenchyma formation through programmed cell death in rice roots under submergence

Nitric oxide (NO) plays a significant role in plants under different abiotic stress. However, the influence of NO and other reactive nitrogen species (RNS) in employing nitrosative stress in rice seedlings under submergence remains unexplored. Submergence also stimulates the development of lysigenous aerenchyma, facilitating oxygen supply to roots but the contribution of NO and RNS in aerenchyma formation under submergence is not known. Present study investigated the major components of the nitro-oxidative stress and their association with lysigenous aerenchyma development in the Sub1 near isogenic line of rice under submergence. Following submergence, Swarna showed increased NADPH oxidase (NOX) activity with excess reactive oxygen species (ROS) production in roots. Submergence also caused increased NO content and membrane lipid peroxidation in Swarna roots. Submergence-induced ROS and RNS accumulation in roots disturbed the redox homeostasis leading to the formation of lysigenous aerenchyma through programmed cell death (PCD). PCD was also accompanied by altered cytoplasmic streaming and DNA damage. In the present study Swarna Sub1 exhibited increased SOD, CAT, POX, APX, GR and GSNOR activity with subsequent detoxification of ROS and RNS; eventually decreasing the aerenchyma formation in root under submerged conditions. Overall, the study established ROS and RNS-mediated unique mechanism in lysigenous aerenchyma formation in rice roots under submergence.

Stevia rebaudiana Bertoni responses to salt stress and chitosan elicitor

This study examined the effect of chitosan elicitor with four different concentrations (0, 0.2, 0.4 and 0.6 g/l) on physiological and biochemical properties of stevia under four levels of salinity stress (0, 50, 100, 150 mM level of NaCl). Salt stress caused reduction of chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophyll, carotenoid and total protein content. The increment of malondialdehyde (MDA) content was not significant in all NaCl levels, while the CAT and POX activities were increased as well as stevioside and rebaudioside A under salinity stress. On one side, chitosan treatments could compensate the reduction of physiological traits such as photosynthetic pigments and protein content. On the other side, chitosan caused multiple increases in malondialdehyde content, antioxidant enzymes activity (catalase and peroxidase), steviol glycosides (stevioside and rebaudioside A) under salt stress. We report for the first time, the potential of chitosan to enhance salinity-tolerant abilities in stevia through increment of the salt-adaptive factors and to diminish harmful damages caused by NaCl stress.

Biotization of Arabidopsis thaliana with Pseudomonas putida and assessment of its positive effect on in vitro growth

Determination of the optimal inoculation method and concentration to use for plant-bacteria interaction studies is important in many cases, such as the phytoremediation of heavy metals and other toxic compounds in contaminated areas. The aim of this study was to compare different concentrations and times of inoculation of Pseudomonas putida with various growth stages of Arabidopsis thaliana in 14-d in vitro cultures. A significant beneficial impact of the bacterium was detected in the shoot length and root weight of seedlings. The highest shoot length and root fresh and dry weights were detected in 14-d and 2 × 103 cfu mL−1 inoculated samples. In addition, the increase in root weight could be visualized with crystal violet staining, as relatively more root hair and lateral root formation occurred in seedlings inoculated with moderate concentrations of bacteria, possibly due to the ability of P. putida to produce indole-acetic acid. Moreover, the highest photosynthetic pigment accumulation was obtained with the highest bacterial inoculum (2 × 106 cfu mL−1), which was tested in 0- or 3-d-old seedlings. Rhizospheric bacterial colonization was also visualized with GFP-labeled bacteria by confocal microscopy. These results showed that biotization of A. thaliana with P. putida KT2440 did not cause severe oxidative stress in seedlings, because H2O2 accumulation levels together with CAT and POX activities were not significantly induced. Therefore, this strain could be used for several applications based on plant-bacteria interactions.

Physiological and antioxidant changes in sunflower seeds under water restriction

Abstract: Seed vigor may be determinant for field performance, especially under water restriction conditions. Sunflower is a crop subject to these conditions in the field and, therefore, the aim of this study was to evaluate the physiological and antioxidant changes in sunflower seeds under water restriction. Two lots of sunflower seeds (cv. Hélio 253) with different vigor levels were used. After initial characterization, seeds were placed to germinate under water potentials of 0.0, -0.2, -0.4, -0.6 and -0.8 MPa and evaluated by tests of germination, first germination count, shoot length and primary root length. The activities of the antioxidant enzymes SOD, CAT, POX and APX were also evaluated at 0, 2, 4 and 6 days after sowing. Water restriction led to a decrease in germination and slower seedling growth, regardless of seed vigor level. SOD activity was similar in the two lots, with reduction in activity four days after sowing. CAT activity was affected differently during germination in the two lots, and it was generally higher in the most vigorous lot. In higher vigor seeds, there was lower POX activity in water restriction treatments compared to the control. In general, seeds of lower vigor have lower capacity for activation of antioxidant enzymes, especially peroxidases.

Integrative application of licorice root extract or lipoic acid with fulvic acid improves wheat production and defenses under salt stress conditions.

Although different plant extracts and plant growth regulators are used as biostimulants to support plants grown under salt stress conditions, little information is available regarding the use of licorice root extract (LRE) or lipoic acid (LA) as biostimulants. Studies on the application of LRE or LA in combination with fulvic acid (FA) as natural biostimulants have not been performed. Therefore, in this study, two pot experiments were conducted to evaluate the potential effects of LRE (5gL-1) or LA (0.1mM) supplemented as a foliar spray in combination with FA (0.2mgkg-1 soil) on osmoprotectants and antioxidants, growth characteristics, photosynthetic pigments, nutrient uptake, and yield as well as on the anatomical features of the stems and leaves of wheat plants irrigated with three levels of saline water (0.70, 7.8, and 14.6dSm-1). Moderate (7.8dSm-1) and high (14.6dSm-1) levels of salinity caused a significant (p≤0.05) increase in the activities of SOD, APX CAT, POX, and GR as well as in electrolyte leakage, malondialdehyde level, and reactive oxygen species (O2‒ and H2O2) levels compared to those in controls (plants irrigated with tap water). However, the leaf relative water content, membrane stability index, NPK uptake, leaf area, plant height, spike length, straw yield, grain yield, and protein content of wheat grains significantly (p≤0.05) decreased. Addition of LRE or LA and/or HA to wheat plants under saline stress significantly (p≤0.05) enhanced their morphological and physio-biochemical characteristics in parallel with increases in the activities of enzymatic antioxidants. Salinity stress altered (p≤0.05) wheat stem and leaf structures; however, treatment with LRE+FA significantly improved these negative effects. These findings indicate that FA+LRE treatment significantly improved the antioxidant defense system of the plants, thereby reducing ROS levels and increasing wheat growth and production under saline conditions.

Silver nanoparticles and silver salt (AgNO3) elicits morphogenic and biochemical variations in callus cultures of sugarcane.

The research work was arranged to check the role of AgNPs and silver ions on callus cells of sugarcane (Saccharum spp. cv CP-77,400). AgNPs were synthesized chemically and characterized by UV-Vis spectra, XRD and SEM. AgNPs and silver ions were applied in various concentrations (0, 20, 40, 60 ppm) to sugarcane calli and the induced stress was characterized by studying various morphological and biochemical parameters. AgNPs and silver ions treatments produced high levels of malondialdehyde, proline, proteins, TP and TF contents. Similarly, CAT, SOD and POX activity was also significant in both treatments. The lower concentration of AgNPs and silver ions (20 ppm) provided maximum intracellular GSH level. This work mainly showed effects of AgNPs and silver ions on sugarcane calli in terms of morphological aberrations and cell membrane damage due to severe oxidative stress and production of enhanced levels of enzymatic and non-enzymatic antioxidants as self-defence to tolerate oxidative stress by scavenging reactive oxygen species. These preliminary findings will provide the way to study ecotoxicity mechanism of the metal ions and NPs in medicine industry and in vitro toxicity research. Furthermore, silver ions alone and their chemically synthesised AgNPs can be used for various biomedical applications in future.

Comparison of Effects of Potassium Iodide and Iodosalicylates on the Antioxidant Potential and Iodine Accumulation in Young Tomato Plants

Iodine (I) is classified as a beneficial element for plants. Until now, there have been only hypotheses regarding the uptakes of organic iodine compounds by plant roots. The purpose of our research was to compare the uptakes and effects of the application of the following mineral and organic iodine compounds on young tomato plants: KI, 5-iodosalicylic (5-ISA), and 3,5-diiodosalicylic (3,5-diISA) acids. An additional control combination included the treatment with salicylic acid (SA) alone. All compounds were introduced into the nutrient solution in 5, 10, 25, and 50 μM I concentrations. It was established that after the application of 5-ISA and 3,5-diISA, iodine is taken up to a smaller extent than from KI. The tested KI, 3,5-diISA, and 5-ISA doses had no negative impact on the growth and development of plants, apart from the reduction of shoot biomass after the application of 3,5-diISA in 10 and 25 µM I doses. All applied compounds, except for SA, caused a reduction of ascorbic acid (AA) content and increase of dehydroascorbic acid (DHA) content in leaves. A significant increase of APX activity was noted only for the highest doses of KI and 5-ISA. None of the iodine compounds, in most tested doses, have substantially increased the CAT and POX activities in tomato leaves. Application of KI decreased the levels of all analyzed sugars in tomato leaves. The effect of iodosalicylates on sugar content varied depending on the compound: when applied in the highest dose 5-ISA increased, while 3,5-diISA decreased the sugar accumulation in tomato plants. In all tested treatments, a reduction of SA content in leaves was noted. We conclude that organic iodine compounds, i.e., 3,5-diISA and 5-ISA, can be taken up by the roots of tomato plants at an early stage of development.

Tobacco plants (Nicotiana benthamiana) were influenced by silicon and were not infected by dodder (Cuscuta europaea)

The effect of silicon (Si) on tobacco (Nicotiana benthamiana) development and dodder (Cuscuta europaea) – tobacco interaction were studied. Three Si application approaches were tested: tobacco seed priming (2.5 mM Si and 5 mM Si; 2.5S, 5S), watering tobacco plants with Si solution (2.5 mM Si and 5 mM Si; 2.5W, 5W) and foliar application (1 mM Si and 2.5 mM Si; 1F, 2.5F). Dodder was not able to infect the host plant in almost all Si treatments. Only in the control and 2.5W treatments was dodder able to infect its host. A significant increase in all observed antioxidant enzymes activities (POX, CAT and SOD) occurred in the plants of 2.5W treatment after infection in comparison with the uninfected 2.5W treatment and control plants, which indicated the importance of antioxidant enzymes activities in the plant parasite – host interaction. Resistance of Si treated plants to dodder could have been due to the changes in the cell wall properties of the epidermis and cortex where activity of POX was confirmed histochemically.The growth and development of tobacco shoots were evaluated after four and eight weeks of cultivation in the individual Si treatments. The development of shoots was enhanced after eight weeks of cultivation in the 2.5S, 5S, 2.5W and 5W treatments in comparison with the control treatment. However, a negative effect of Si was observed in 1F and 2.5F treatments. In the majority of cases, the plants treated with Si had decreased chlorophyll content when compared to control, except for chl a in 5W plants after 8 weeks of cultivation. Contrary to this, carotenoids increased in all Si treated plants after eight weeks cultivation in comparison with the control. The secondary xylem formation in tobacco was enhanced after 4 and 8 weeks cultivation in shoots of plants receiving the 2.5S, 5S, 2.5W and 5W treartments. The cambium was the most active in producing secondary xylem in the 2.5S treatment. Protein profile and antioxidant enzymes activities (POX, CAT and SOD) were altered by Si treatment. After 8 weeks of cultivation, activities of POX were significantly decreased in 2.5S, 5S, 2.5W and 5W in comparison with control. Catalase was decreased in 2.5S, 5S and 5W in comparison with the control, however, 1F and 2.5F treatments had significantly increased CAT and SOD activities. The specific activity of POX was confirmed histochemically in Si treated plants in the cell walls of several stem tissues like the epidermis, cortex and pith. A small amount of H2O2 was detected in leaves in the control and Si treated plants. The amount of O2− decreased in all treatments with time. The highest Si concentration in the plants (almost 800 mg . kg−1 d. w.) was detected in the 2.5W, 5W treatments.

One-pot synthesis of a composite consisting of the enzyme ficin and a zinc(II)-2-methylimidazole metal organic framework with enhanced peroxidase activity for colorimetric detection for glucose.

An enzyme-metal organic framework (MOF) composite with saucer-like structure was prepared via one-pot synthesis from ficin (a cysteine proteolytic enzyme with POx activity), zinc(II) ions and 2-methylimidazole. The composites exhibit a 2.5-fold higher catalytic activity and stronger affinity for substrates compared to free ficin. This was exploited to design a colorimetric assay for the determination of glucose. The addition of glucose oxidase causes the formation of H2O2 which is catalytically oxidized by ficin to form a blue coloration that can be measured at 652nm. The assay has a 0.12μM detection limit and excellent selectivity. It was successfully applied to the determination of glucose in diluted serum samples. Graphical abstract Schematic presentation of the synthesis process and the enhanced peroxidase activity of ficin@MOF composites. Ficin was immobilized in a new saucer-like shape of Ficin@MOF composites, which showed higher peroxidase activity than free ficin. Scheme and graphical abstract contains poor quality of text.We have attach a new picture with 600 dpi as scheme and graphical abstract.

The roles of sodium nitroprusside, salicylic acid, and methyl jasmonate as hold solutions on vase life of Gerbera jamesonii ‘Sun Spot’

TThe present study investigates the roles of nitroprusside (SNP), salicylic acid (SA), methyl jasmonate (MJ), and their interaction with 8-hydroxyquinoline sulfate (8-HQS) in regulating the peroxidase activity (POX), water uptake, the relative water content (RWC), the contents of malondialdehyde (MDA), soluble sugar, proline, and protein content in the petals and the stem bending of Gerbera jamesonii ‘Sun Spot’ cut flowers. Cut flowers were treated with various concentrations (50, 100, and 200 µM) of hold-solutions containing 8-HQS, SA, MJ, and SNP. Hold solutions were used alone or in combination with 100 µM 8-HQS for 24 h. Distilled water was used as control and sucrose (4%, w/v) was added to all solutions. The findings showed that 50 µM SA+ 100 µM 8-HQS markedly improved the RWC, the contents of proline, anthocyanin, carotenoid, protein, and soluble sugar, and activities of POX in the petals and markedly reduced water loss and the contents of MDA in the petals, compared with other treatments, especially the control. Meanwhile, the combination of plant growth regulators (PGR) with 8-HQS markedly improved positive indexes than use alone PGR. This phenomenon seemed to be due to more absorption of PGR. Among different concentrations of PGR, 50 μM is the most effective treatment for the improvement of the vase life of Gerbera jamesonii cut flowers. The results also demonstrated that SA+8-HQS improves the vase life of gerbera cut flowers by enhancing the membrane stability and water retaining capacity as well as increasing proline, antioxidant activity, and pigment contents.

Licorice Root Extract Boosts <i>Capsicum annuum</i> L. Production and Reduces Fruit Contamination on a Heavy Metals-Contaminated Saline Soil

Natural supplementations are used in agriculture nowadays not only for improving plant performance but also for reducing the contamination of plant edible parts. Two field trials were conducted to study the potential effects of licorice root extract (LRE; 0.5%) on performance, physio-biochemical components, antioxidant defense system, and contaminants concentrations of Capsicum annuum L. plants grown on a saline soil contaminated with heavy metals. LRE was applied in single (i.e., as rhizosphere application with drip irrigation water; -RA or as foliar spray; -FA) or in integration (i.e., LRE-RA + LRE-FA) treatment. The results showed that both single or integrative treatments significantly increased plant growth and yield, leaf concentrations of photosynthetic pigments, free proline, total soluble sugars, N, P, and K+, ratio of K+/Na+, and activities of CAT, POX, APX, SOD and GR, while significantly reduced contaminants; Na+, Cd, Cu, Pb and Ni concentrations in plant leaves and fruits on heavy metals-contaminated saline soil compared to the control (without LRE). Additionally, the integrative LRE-RA + LRE-FA treatment significantly exceeded both single treatments in this concern, which had been recommended for maximizing pepper plant performances with minimizing heavy metals in fruits on contaminated saline soils.

Licorice Root Extract Boosts <i>Capsicum annuum</i> L. Production and Reduces Fruit Contamination on a Heavy Metals-Contaminated Saline Soil

Natural supplementations are used in agriculture nowadays not only for improving plant performance but also for reducing the contamination of plant edible parts. Two field trials were conducted to study the potential effects of licorice root extract (LRE; 0.5%) on performance, physio-biochemical components, antioxidant defense system, and contaminants concentrations ofCapsicum annuumL. plants grown on a saline soil contaminated with heavy metals. LRE was applied in single (i.e., as rhizosphere application with drip irrigation water; -RA or as foliar spray; -FA) or in integration (i.e., LRE-RA + LRE-FA) treatment. The results showed that both single or integrative treatments significantly increased plant growth and yield, leaf concentrations of photosynthetic pigments, free proline, total soluble sugars, N, P, and K+, ratio of K+/Na+, and activities of CAT, POX, APX, SOD and GR, while significantly reduced contaminants; Na+, Cd, Cu, Pb and Ni concentrations in plant leaves and fruits on heavy metals-contaminated saline soil compared to the control (without LRE). Additionally, the integrative LRE-RA + LRE-FA treatment significantly exceeded both single treatments in this concern, which had been recommended for maximizing pepper plant performances with minimizing heavy metals in fruits on contaminated saline soils.

Effect of Heat Stress on Antioxidative Defense System and Its Amelioration by Heat Acclimation and Salicylic Acid Pre-Treatments in Three Pigeonpea Genotypes

In this study, effect of heat stress on antioxidative defense system and its amelioration by heat acclimation and salicylic acid pre-treatments in three pigeonpea genotypes at seedling stage was analyzed. Heat acclimation (45°C for 3h) and salicylic acid (0.5 mM and 1 mM for 3h) pre-treatments were given to seven days old seedlings. Heat stress resulted in oxidative stress through the production of reactive oxygen species (ROS) mainly H2O2 and increased peroxidation of lipid membranes (MDA content). These pre-treatments conferred protection against heat stress through reduction in MDA and H2O2 content by means of induced adaptation effect and antioxidant activity which enhanced tolerance towards heat stress. Antioxidative defense system was observed through increased activity of CAT (average 1.02 fold increase in heat acclimated, 0.77 fold in 0.5 mM SA and 1 fold in 1 mM SA) and POX (average 1.30 fold increase in heat acclimated, 1.24 fold in 0.5 mM SA and 1.37 fold in 1 mM SA) in all genotypes. Among the three genotypes, AL 1931 performed best and acquired maximum thermotolerance.

Biochemical changes during flowering in Citrus species

The present experiment was conducted during 2017–2018 with the objective to understand the relationship of seasonal changes in biochemical traits with the flowering behaviour of acid limes (Pusa Udit, Pusa Abhinav and ALC-29), lemons (Konkan Seedless, Kagzi Kalan and Hill lemon) and sweet oranges (Pusa Sharad, Pusa Round and Mosambi). Sweet oranges and Hill lemon expressed flowering once (February to March), and lemons and Acid limes bloomed almost round the year. In all lemons (except Hill lemon) and limes, protein level ≥ 9.30 mg g−1 FW promoted the flowering, however, it was ≥ 19.3 mg g−1 FW in Hill lemon and sweet oranges. In lemons and limes, superoxide dismutase (SOD) activity ≥ 9.88 Unit mg−1 min−1 TSP expressed the association with flowering except Pusa Abhinav lime. Hill lemon and sweet oranges bloomed at the activity of SOD ≥ 13.77 Unit mg−1 min−1 TSP. The catalase (CAT) activity did not follow a systematic pattern in most of the cultivars. In limes and lemons (except Hill lemon), the plants showing POX activity ≥ 17.77 μmol min−1 mg−1 total soluble proteins (TSP) showed flowering, while in rest of the genotypes, its level was ≥ 52.45 μmol min−1 mg−1 TSP to initiate the flowering. In most of the limes and lemons during August to February, ascorbate peroxidase (APOX) activity ≥ 0.20 μmol min−1 mg−1 TSP favoured the flowering, however, in Hill lemon and sweet oranges, it was ≥ 0.220 μmol min−1 mg−1 TSP. The lower activity of O2−(0.91–1.76 μmol g−1 FW) between August to January in limes and lemons (except Hill lemon) promoted the flowering.

Gamma irradiation enhancement of biofilm production in Bacillus amyloliquifaciens and effect of mutants’ inoculation on APX1 expression in salt-stressed Egyptian barley

Gamma rays are known to induce random mutations, which are used to enhance the production of biofilms in bacteria. Therefore, to improve the activity of biofilm formation in wild Bacillus amyloliquefaciens (HM6), this bacterial strain was mutated using five doses of gamma irradiation. Sixteen mutants and their wild strain B. amyloliquefaciens (HM6) were tested for biofilm formation under two different (250 and 350 mM) NaCl concentrations. Only six mutants exhibited a significant increase in biofilm formation under 350 mM NaCl. Inoculation of salt-stressed Giza123 barley seedlings with the two mutants (M1 and M7), which showed distinguishable rep-PCR patterns, and their wild strain significantly decreased MDA content. In addition, such inoculation inhibited POX and CAT activities, while AsA content was increased. The lowest POX and CAT activities, as well as the highest AsA content, were recorded with mutant M7. The full length cDNA of Giza123 APX1 was cloned, sequenced, and submitted to GenBank under accession number MF804856. In BLASTX analysis, its sequence exhibited 99% homology with the Hordeum vulgare peroxisome type ascorbate peroxidase. RT-PCR revealed variable APX1 expression levels in the stressed and nonstressed Giza123 seedlings. Salt stress upregulated the APX1 expression level in uninoculated?stressed seedlings compared to the uninoculated?unstressed ones. On the other hand, inoculation with M1 and M7 mutants and their wild strain modified the APX1 expression level, where the wild and the M1 mutant downregulated the APX1 expression level, while mutant M7 upregulated its expression level under salt stress.

The insecticidal activity of Satureja hortensis essential oil and its active ingredient -carvacrol against Acrobasis advenella (Zinck.) (Lepidoptera, Pyralidae)

Nowadays, Acrobasis advenella is considered a pest of the highest economic significance in black chokeberry plantations, negatively affecting the quantity and quality of fruits. The aim of this study was to investigate the effect of Satureja hortensis essential oil and its main constituent, carvacrol, on the life cycle and physiology of A. advenella. The metabolic activity of both preparations was evaluated against insect α- and β- glucosidase, catalase, peroxidase and polyphenol oxidase. The results showed S. hortensis essential oil and carvacrol, are characterized by insecticidal activity against A. advenella larvae. It found an increase in catalase activity in A. advenella homogenates under the influence of carvacrol and an induction of polyphenol oxidase by S. hortensis EO with no changes in POX activity. Also, it was shown that the activity of α- and β-glucosidase significantly increased in larvae fed on inflorescences treated with the essential oil and carvacrol. These preparations particularly strongly affected β-glucosidase activity in the insect homogenates. S. hortensis essential oil reduced emergence the longevity of moths. The obtained results suggest that S. hortensis essential oil and carvacrol can be useful in protecting organic crops of black chokeberry but essential oils may be more effective biopesticides than their active ingredients separately.

Microtopography Alters Hydrology, Phenol Oxidase Activity and Nutrient Availability in Organic Soils of a Coastal Freshwater Forested Wetland

Hummock-hollow microtopography is a unique feature of wetland ecosystems, but our understanding of its effects on soil carbon and nutrient cycling is limited. We investigated effects of microtopography on hydrology, phenol oxidase activity (POX) and nutrient availability in a freshwater forested wetland of coastal North Carolina. Water table depth (WTD) was measured from September 2012 to August 2013. Ion exchange probes were used to measure nutrient concentrations prior to soil sample collection in August 2013. WTD fluctuated seasonally with maximum and minimum WTD resulting in 92% (September 2012) to 8% (June 2013) of the site in flooded and non-flooded conditions, respectively. Hummocks had greater POX activity (12 ± 2.8 μmol g−1 h−1) compared to hollows (4 ± 0.7 μmol g−1 h−1) and greater concentrations of potassium and sulfur, but lower concentrations of calcium, iron, zinc, boron, and lead. POX was negatively correlated with soil water content. Higher enzyme activity in hummocks likely drives greater rates of carbon and nutrient cycling compared to hollows, consistent with observations that hummocks are hotspots for CO2 fluxes. Microtopography altered site-level hydrologic conditions, phenol oxidase activity and nutrient availability with important implications for understanding carbon and nutrient cycling in forested wetlands and response to changes in hydrology.

Integrative moringa and licorice extracts application improves Capsicum annuum fruit yield and declines its contaminant contents on a heavy metals-contaminated saline soil

Green approaches for improving plant performance using natural supplementations are highly seeking. Following a preliminary study conducted on contaminated saline (EC = 7.75 dS m−1) and normal (EC = 1.4 dS m−1) soils, two main field trials were conducted to study the potential effects of licorice root (LRE; 0.5%) and moringa seed (MSE; 0.5%) extracts, supplemented to soil through irrigation water (SA) and/or as foliar spray (FS), on performance, physio-biochemical components, antioxidant defense system, and contaminants contents of Capsicum annuum plants grown on heavy metals-contaminated saline soil. Both extracts were applied in single treatments such as LRE-SA, MSE-SA, LRE-FS, and MSE-FS or in integrations like LRE-SA+LRE-FS, LRE-SA+MSE-FS, MSE-SA+LRE-FS, and MSE-SA+MSE-FS. The preliminary study results showed significant reductions in plant performance (growth and yield), chlorophylls content and significant increase in Cd content due to heavy metals and salt stress. However, LRE and MSE applied singly or in combinations positively modified these parameters compared to the control (SA and FS were applied with tap water). On the other hand, these parameters were not responded to LRE and/or MSE applications on the normal soil. The main studies results showed that all single or integrative treatments significantly increased plant growth and yield, leaf contents of leaf photosynthetic pigments, free proline, total soluble sugars, N, P, and K+, ratio of K+/Na+, and activities of CAT, POX, APX, SOD, and GR. In contrast, contaminants; Na+, Cd, Cu, Pb and Ni contents in plant leaves and fruits were significantly reduced on heavy metals-contaminated saline soil compared to the control. Additionally, all integrative treatments significantly exceeded all single treatments in this concern. The integrative MSE-SA+LRE-FS was the best treatment that is recommended to be used to maximize pepper plant performances and minimize plant contaminant contents on contaminated saline soils.

Lipopolysaccharide-induced priming enhances NO-mediated activation of defense responses in pearl millet challenged with Sclerospora graminicola.

Lipopolysaccharide (LPS) elicitors isolated from Pseudomonas fluorescens UOM SAR 14 effectively induced systemic and durable resistance against pearl millet downy mildew disease caused by the oomycete Sclerospora graminicola. Rapid and increased callose deposition and H2O2 accumulation were evidenced in downy mildew susceptible seeds pre-treated with LPS (SLPS) in comparison with the control seedlings, which also correlated with expression of various other defense responses. Biochemical analysis of enzymes and quantitative real-time polymerase chain reaction data suggested that LPS protects pearl millet against downy mildew through the activation of plant defense mechanisms such as generation of nitric oxide (NO), increased expression, and activities of defense enzymes and proteins. Elevation of NO concentrations was shown to be essential for LPS-mediated defense manifestation in pearl millet and had an impact on the other downstream defense responses like enhanced activation of enzymes and pathogen-related (PR) proteins. Temporal expression analysis of defense enzymes and PR-proteins in SLPS seedlings challenged with the downy mildew pathogen revealed that the activity and expression of peroxidase, phenylalanine ammonia lyase, and the PR-proteins (PR-1 and PR-5) were significantly enhanced compared to untreated control. Higher gene expression and protein activities of hydroxyproline-rich glycoproteins (HRGPs) were observed in SLPS seedlings which were similar to that of the resistant check. Collectively, our results suggest that, in pearl millet-downy mildew interaction, LPS pre-treatment affects defense signaling through the central regulator NO which triggers the activities of PAL, POX, PR-1, PR-5, and HRGPs.